The invention relates to a method and a device for the contactless determination of an electrical potential of an object using one electrode or a first electrode and a second electrode.
It is known practice to contactlessly measure the current flow through an object. This may be effected using inductive coupling, the Hall effect or the GMR (Giant Magneto Resistance) effect. However, in order to be able to contactlessly measure electrical power, a method for contactless potential measurement is also required in addition to the contactless current measurement. Contactless potential measurement, in particular of high voltages, is particularly important, in particular, in the field of smart metering, smart grid and response-demand strategies.
So-called electric field meters provide one possibility for this. Said meters use the effect of electrostatic induction in order to be able to infer the voltage to be determined using the determined electrical field strength. However, for this purpose, the distance between the object, whose potential is intended to be determined, and the measuring electrode of the electric field meter as well as the material (dielectric) between the measuring electrode and the object in the measuring capacitance must be exactly known. In order to be able to use an electric field meter to also measure DC voltages, a shutter (field diaphragm) in the form of a chopper (impeller) is generally used between the measuring electrode and the object.
Capacitive voltage dividers can also be used to determine pure AC voltages, in which case the coupling capacitance between a reference electrode and the potential to be measured must likewise be known here.
Both methods and devices (electric field meter and capacitive voltage divider) presuppose accurate knowledge of the coupling to the voltage to be measured, in particular the distance between the measuring electrode and the measurement object. In this respect, these known methods are unsuitable for only temporary measuring operations or subsequent measuring installations. Electric field meters and capacitive voltage dividers are permanently installed for precise measurements and are calibrated in the installation environment. In the case of handheld measuring devices, exact knowledge of the geometry and material composition (line installation, air, gas, condensation, etc.) of the measuring set-up is required. For this purpose, special spacers, for example, are used in commercially available electric field meters. However, spacers have the disadvantage that, in order to determine the potential of electrically insulated lines in particular, they do not sit directly on the conductive material and therefore set the distance only with inadequate precision. In addition, the type of insulating material cannot be taken into account. If this precision of the known contactless potential measuring methods does not suffice, measurement must usually be carried out using contact.